Study: Cannabis «modestly» effective against multiple sclerosis

American researchers have analyzed 28 recent studies, to assess the current state of scientific knowledge regarding the effectiveness of cannabis in treating multiple sclerosis. This method—a meta-analysis—reaches a surprising conclusion. Compared to treatments with an equivalent dose of THC/CBD, «The short-term neurological effects in patients are either mild, limited, or moderate, and the benefits are detected more through subjective reports than objective measurements.". »

This finding reinforces an existing criticism: the drug Sativex—which uses an equal THC-to-CBD ratio—is not effective enough. It is approved in the European Union, the United Kingdom, and Canada, but not in the United States. In France, it is legal but is not not prescribed to patients in part because of its low yield.

According to the meta-analysis, this type of treatment works «in a therapeutic window limited to modestly improving, subjectively, spasticity, pain, bladder problems, and sleep issues in the patients observed. In addition, scientists have observed benefits only «in the first few weeks after starting treatment.».

A 3-point decrease in pain on a scale of 10

To reach this scathing conclusion, the researchers dug into their archives. They pulled out 28 studies published between 2007 and 2021. The American scientists claim to have «no conflict of interest», nor did they receive any external funding for this work. Therefore, their results are «reviewed and approved» by other scientists, as is customary.

In addition to whether or not cannabis is effective, the researchers analyzed the methodology of other scientific studies. They identified two significant biases. The first: half of the studies involved mice rather than humans. «The validity of the animal studies »is less certain, due to differences in the endocannabinoid system" between humans and mice, they point out.

Another drawback: many patients who do not experience a positive effect from cannabis drop out of the study before it ends. Logically, this skews the results. If only patients who experience a positive effect remain, then the study will conclude that cannabis is effective.

In human trials, nine studies have shown positive results. Patients reported a 2.8-point reduction (on a scale of 0 to 10) in spasticity, the main consequence of multiple sclerosis. In addition, five other studies report a 3.4-point reduction (out of 10) in pain levels thanks to cannabis.

In conclusion, the meta-analysis calls on scientists to raise the bar. Their studies must be «high-quality, long-term, randomized, double-blind studies with a control group receiving a placebo.». Without cutting-edge research, the «Confidence in the effectiveness of cannabis for multiple sclerosis» could erode.